Comparison of Dietary Lipid Source and Levels (Fish oil and Beef tallow) on the Growth and Cold Resistance for Cobia (Rachycentron canadum)

• Main Authors: Zhi Zhong Hsu, 許志仲
• Other Authors: Chyng Hwa Liou
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/85719533545964512679

碩士 === 國立海洋大學 === 水產養殖學系 === 90 === Abstract The purpose of the study was to investigate different lipids and levels on the cold tolerance, growth and fatty acid composition of cobia. In the experiment, juvenile cobia (Rachycentridae canadum) (70±10 g) held in aquaria were fed eight diets of 5、10、 15% fish oil and tallow respectively and a mixture of 5﹪of the two lipids. Weight gain of fish fed the diet containing 10% fish oil was the best and that containing 5% tallow was significantly lower than others. Culture temperature was initially 25℃ and then was successively reduced to 21℃ by 1℃ per day. The temperature was kept for a week, then was successively reduced to 13 ℃ by 1℃ per day and the temperature was kept to test cold tolerance of cobia. Fatty acid composition of red cell, plasma, liver, dorsal and ventral muscle were analyzed. Cold tolerance results indicate that the half lethal time of fish fed the diet cont aining 5﹪and 10﹪fish oil was higher than other group 6 to 14 hours , the mixture group was the lowest and the other group was similar. The average of accumulated half lethal time and all lethal time of fish fed diet containing 10% fish oil was the highest among the test diet groups, however, that of 15% fish oil was almost the lowest. In addition, temperature and diets on different tissue fatty acid composition of the cobia were analyzed. Red cell and plasma fatty acid composition were affected by temperature and liver, dorsal and ventral fatty acid composition were affected by diets. In low temperature, cobia can convent C18:0 to C18:1n-9 and n-3 to fatty acid C22:6n-3.It is assumed that cobia increase the unsaturation to adapt low temperature environment